The present invention relates to a voltage regulator and the related regulating method, and more particularly to a high speed and low cost voltage regulator, and the related regulating method.
In a system having multi-circuit blocks, a voltage regulator may be used to provide a supply voltage to the multi-circuit blocks according to an output voltage provided by a power source. Therefore, the voltage regulator should be able to provide currents to the multi-circuit blocks while keep the supply voltage intact during the operation of one or more of the multi-circuit blocks. For example, a low dropout (LDO) regulator having low-dropout between the output voltage of the power source and the supply voltage is commonly used to provide the power for the multi-circuit blocks coupled thereto. However, for the circuit device fabricated under the modern semiconducting process, the operation voltage of the system is low. Then, there may not have enough room, i.e. the so called headroom, for the voltage dropout between the LDO regulator and the circuit block. Moreover, the conventional LDO regulator normally comprises two stages, and it is well-known that a two stage system always suffers from the stability problem. In other words, the conventional LDO regulator may not be a stable system during the high speed operation.
Another example to provide a stable supply voltage to the multi-circuit blocks is to use a large capacitor to connect to the output node of the power source in order to become a charges pool at the output node of the power source. However, this may occupy large chip area of the circuit system if the capacitor is an on-chip capacitor; and if the capacitor is an off-chip capacitor, the bond wire of the off-chip capacitor may become an inductive element under the high frequency. Therefore, using a large capacitor as a charges pool at the output node of the power source is also not a good solution to provide a stable supply voltage to the multi-circuit blocks.
Accordingly, providing a novel voltage regulator to solve the headroom problem and the high frequency problem of the conventional regulator is an urgent problem in this field.